Given the multitude of nematodes associations with invertebrate and vertebrate hosts, the beetle associated Pristionchus pacificus nematode represents a much needed knowledge bridge between the free-living soil nematode Caenorhabditis elegans and many disease causing filarial nematodes such as Brugia malayi and Wucheria bancrofti. While recent advances in insect pheromone recognition were conducted on insects regarding intraspecies interactions, primarily in mating, we know very little about the components needed to mediate interspecies interactions between nematodes and insects, the latter being a significant vector for spreading human diseases. Specifically, how does chemosensation toward a particular compound become reprogrammed during speciation, and how much does this influence the nematodes' host preferences? Aside from C. elegans, P. pacificus is the only other nematode in which a forward genetic approach is feasible. We have therefore carried out the first behavioral genetic screen in P. pacificus for lack of chemotaxis toward a known oriental beetle pheromone, ZTDO, and isolated two Oriental Beetle pheromone Insensitive mutants: obi-1 and obi-3. Obi-1 and obi-3 are specifically unable to chemotaxis toward ZTDO but are wildtype in chemotaxis toward other attractants. We will identify the molecular lesions of obi-1 and obi-3 and mis-express the P. pacificus wildtype genes using C. elegans winged amphid neuron promoters such as odr-7 and str-2 (specific for AWA and AWC, respectively) and look for gain-of-function attraction chemotaxis phenotype towards ZTDO in C. elegans. Thus we will attempt to engineer a new chemosensory output into C. elegans and thereby determine the genes required for reprogramming chemosensory behavior. The molecular mechanisms for how human parasitic nematodes sense their host environments has largely been extrapolated from the free-living C. elegans, but may be more closely modeled by the arthropod associated P. pacificus that senses insect host pheromones. This proposal outlines the first olfaction behavioral screen in P. pacificus and aims to understand the specific developmental and neurophysiological factors mediating Pristionchus attraction to a pheromone using a combination of molecular and genetic approaches. PUBLIC HEALTH RELEVANCE: The molecular physiology of insect pheromone attraction will have a direct impact on our understanding of olfaction in nematodes, as well as chemosensation in general. Our proposal has the potential to be translated into improving treatments against parasitic nematodes by targeting their means of perceiving their environment and to elucidate the overall diversity of molecular pathways in animal chemosensation.